With development of mobile Internet and popularization of intelligent terminals, data traffic increases rapidly. With advantages of a high rate and low costs, a wireless local area network (WLAN) has become a mainstream mobile access technology. Compared with low frequency bands on which spectrum resources are becoming increasingly insufficient, for example, 2.4-GHz and 5-GHz frequency bands, a 60-GHz frequency band has abundant spectrum resources and can easily offer a Gbps-level service throughput. For example, an Institute of Electrical and Electronics Engineers (IEEE) 802.11ad system working on the 60-GHz frequency band can reach a peak rate of 6.7 Gbps. Directional transmission is one of typical features of high frequency communication. When radio is transmitted on a high frequency band, a signal path loss is relatively high, and a capability of penetrating an obstacle is relatively poor. In addition, a high frequency signal has a millimeter-level short wavelength. This is suitable for deploying an array antenna based on an existing radio frequency chip size. A station (STA) in the 802.11ad standard is provided with array antennas, and the array antennas communicate with each other by using a directional link that is generated by using a beamforming (BF) technology and suppress a high path loss by using directional beam gains. To obtain directional beam gains, orientations of receive/transmit beams at two ends of a link need to be adjusted to align beams. When beams at the receive end and the transmit end are not aligned, the beams are mismatched, causing a lack of directional beam gains and dramatic deterioration of quality of a received signal, and consequently, the link is interrupted. To maintain beam alignment at two ends of a link, in the 802.11ad standard, a beam training method is provided. When beams at the receive end and the transmit end are not aligned, a beam training process is initiated. In addition, when beams at the receive end and the transmit end are aligned and a directional link is set up, usually, whether beam mismatching occurs is determined based on whether quality of a received signal dramatically deteriorates or whether the link is interrupted. If the beam mismatching occurs temporarily, the mismatching disappears after a short period of time. In this case, there is no need to initiate a beam training process immediately. In view of this, time for initiating beam training becomes a problem that needs to be resolved currently.
Because the 802.11ad standard supports only SISO(Single-Input Single-Output, SISO) between STAs, a pair of STAs may obtain a directional link after a beam training process. In terms of time for initiating beam training, a currently-provided directional link maintenance solution is as follows. The STAs allocate a counter to the directional link and set an initial value, for example, 126 ms. After the counter is assigned the value, the value of the counter decreases as time passes. When the value of the counter is zero or close to zero, the directional link corresponding to the counter reinitiates a beam training process at a transmit end. In addition, in an existing solution, after the pair of STAs successfully exchange information once on the directional link, the value of the counter may be restored to the initial value, and the value of the counter is updated.
In the existing solution, update of the value of the counter depends on the interactive information obtained by the STAs on the directional link. However, when a quantity of STAs is increased, average opportunities for each STA to use the directional link are reduced, affecting update frequency of the value of the corresponding counter and further affecting accuracy and timeliness of directional link availability determined by the STA.